Poromeric materials are widely used for many different polishing applications. Poromerics are textile-like materials that usually contain a urethane-based impregnation or coating having a multitude of pores or cells. Use of these materials is particularly prevalent in the semiconductor industry.
Many poromeric materials used for polishing are similar to the material described in U.S. Pat. No. 3,284,274. It is believed that large macropores or cells present in the material act to hold slurry and thus aid the polishing process. U.S. Pat. No. 3,504,457 describes the use of these materials in polishing silicon semiconductor substrates.
U.S. Pat. No. 4,841,680 describes a poromeric polishing pad having a working surface comprised of a microporous polymeric material which contains open cells that have their largest opening at the work surface and are deep enough to carry a relatively large quantity of slurry. The pad is made by conventional solvent/nonsolvent polymer coagulation technology.
In addition to poromerics, polymers have been formed into nonporous polishing pads.
Both porous and nonporous prior art polishing pads exist that are formulated from either polyester or polyether polyurethanes. Each material has unique characteristics favorable for specific polishing applications. Polyethers are more hydrolitically stable and are typically used when a high degree of smoothness and planarity are needed. Polyesters are not as hydrolitically stable but are more hydrophilic. More hydrophilic materials are more readily wet and therefore facilitate the flow of polishing fluid. Polyesters also typically require less pad conditioning.
A pad that contains characteristics of both polyesters and polyethers would be beneficial.